PHP uses explode split string for beginners easy to ignore problems explained

1.explode Method Description

The Explode method allows a string to be split into groups by one string as a boundary point.

Array explode (string $delimiter, string $string [, int $limit])

Returns an array of strings, each of which is a substring of string, separated by the delimiter as the boundary point.

parameter Description:
delimiter
The delimited character on the boundary.

string
The input string

Limit
If the limit parameter is set and is a positive number, the returned array contains a maximum of limit elements, and the last element will contain the remainder of the string.
If the limit parameter is a negative number, all elements except the last-limit element are returned.
If limit is 0, it will be treated as 1.

2. Example

Use, split string

<?php$str = ' 1,2,3,4,5,6,7,8,9 ', $arr = explode (', ', $str), Echo ' <pre> ';p rint_r ($arr), echo ' </pre> ';? >

Output:

Array (    [0] = 1    [1] = 2    [2] = 3    [3] = 4    [4] = 5    [5] = 6    [6] = = 7
  
   [7] + 8    [8] = 9)
  

Use, split string, limit is positive

<?php$str = ' 1,2,3,4,5,6,7,8,9 '; $arr = explode (', ', $str, 5), Echo ' <pre> ';p rint_r ($arr), echo ' </pre> ';? >

Output:

Array (    [0] = 1    [1] = 2    [2] = 3    [3] = 4    [4] = 5,6,7,8,9)

Use, split string, negative limit

<?php$str = ' 1,2,3,4,5,6,7,8,9 '; $arr = explode (', ', $str,-3), echo ' <pre> ';p rint_r ($arr), echo ' </pre> ';? >

Output:

Array (    [0] = 1    [1] = 2    [2] = 3    [3] = 4    [4] = 5    [5] = 6)

Use, split string, limit is 0

<?php$str = ' 1,2,3,4,5,6,7,8,9 '; $arr = explode (', ', $str, 0), Echo ' <pre> ';p rint_r ($arr), echo ' </pre> ';? >

Output:

Array (    [0] = 1,2,3,4,5,6,7,8,9)

3. Easy to ignore problems

In general, we use explode to split data such as ID strings.

<?php$ids = ' 1,2,3,4 '; $data = explode (', ', $ids); if ($data) {    foreach ($data as $k + = $v) {        //do Sth    }}? >

Under normal circumstances, IDS is not empty, look at the code will not find any problem, because there is a judgment if (data), it is generally considered to have done an empty processing.
But the reality is ids=null, but data is not empty, causing problems with the code executing in foreach.

<?php$ids = null, $data = Explode (', ', $ids), if ($data) {    print_r ($data);} else{    echo ' null ';}? >

Because Ids=null, the array ( [0] = =) instead of array ()is derived using explode.

So the judgment needs to be modified to avoid problems.

<?php$ids = null, $data = Explode (', ', $ids), if (Isset ($data [0]) && $data [0]) {    foreach ($data as $k + = $v) {        //do sth    }}?>

This article explains PHP use explode split string novice easy to ignore the problem, more relevant content please focus on PHP Chinese web.

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